1. Field of the Invention
This invention relates to devices and a method for forming a pressure seal between two planar sealing surfaces and more particularly to such a device and method which include a toroidal, crushable seal member and a spacer unit for positioning the seal member between the planar sealing surfaces and for controlling the deformation of the seal member as it is crushed between the sealing surfaces.
2. Prior Art
There are many types of equipment which require the formation of a pressure tight seal between confronting planar sealing surfaces. Such equipment includes, for example, pump housings, high pressure fluid conduits, and pressure vessels. Often the confronting planar sealing surfaces are formed on annular flanges which are bolted together. It is common practice to use organic or inorganic gaskets or "O" rings to form such seals and to provide annular grooves in one or both of the confronting planar sealing surfaces to position the seal member. There is a tendency in many such installations for the flanges to bend about the pivot formed by the edge of the gasket or the "O" ring.
One type of installation in which a pressure tight seal is required between confronting planar sealing surfaces is the pressure vessel of a nuclear reactor. The upright cylindrical pressure vessel terminates at its upper end in a radially outwardly extending flange to which is bolted a complimentary flange on the hemispherical vessel head. In order to provide a seal to withstand the two to three thousand psi pressures developed in the pressure vessel with adequate safety margins, a crushable, tubular, metallic torus is typically inserted between the flanges. As the bolts are tightened to draw the flanges toward each other, the crushable tubular metallic torus is deformed to form the pressure tight seal. Annular grooves in the flanges position the torrus and prevent it from slipping as the bolts are tightened. Holes in the inner surface of the tubular torrus, admit reactor coolant into the tubular seal to pressurize it.